Apparatus and method for photovoltaic module with tapered edge seal

ABSTRACT

A photovoltaic module generates electrical power when installed on a roof. The module is constructed as a laminated sandwich having a transparent protective upper layer adhered to a photovoltaic layer. The photovoltaic layer is adhered to the top of a rigid layer, preferably formed from a fiber reinforced plastic. A tapered edge seal is disposed about the peripheral outer edge of the module, so that water and debris easily run off. Preferably, the tapered edge seal is disposed adjacent the photovoltaic layer, and above the rigid substrate layer. The tapered edge seal is thinner at the outer peripheral portion thereof than at a portion thereof adjacent the photovoltaic layer. The laminated module preferably has a layer of double sided tape on the bottom to adhere the module to the surface of a roof.

This application is a continuation of U.S. patent application Ser. No.14/454,226 filed Aug. 7, 2014, the contents of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to solar modules for generating electricalenergy, and more particularly to photovoltaic modules integrated into alaminated, weather resistant sandwiched module for installation onroofs, and more particularly to apparatus and method for edge seals forsuch photovoltaic modules.

2. Description of the Related Art

Conventional photovoltaic modules for generating electrical power forresidences and businesses are often flat and are placed on a portion ofa roof that is exposed to the sun. Historically, such modules wereplaced on structures erected on the roof to support and protect themodules. More recently, photovoltaic modules have become available thatcan be mounted directly on a flat or tilted roof. See, for example, USPatent Application Publication No. 2005/0178248 A1 to Laaly et al., (theentire contents of which are incorporated herein by reference), whichdiscloses a module that incorporates a roofing membrane into the modulestructure. The module is intended to be installed on a new roof orreplacement roof with the membrane providing moisture protection for theunderlying structure as well as providing electrical power.

See also U.S. Pat. Nos. 7,531,740 and 7,557,291 both to Flaherty, etal., the entire contents of both of which are incorporated herein byreference. These patents disclose such photovoltaic modules for roof-topinstallation.

A problem with above mentioned direct roof top attached crystallinesilicon photovoltaic cell based solar modules is their tendency toretain water or other deleterious solids and/or liquids around the edgeseals. See, for example, FIG. 2 of U.S. Pat. No. 7,531,740. After arain, or after a cleaning with water and chemicals, such liquids and/orsolids are often retained in the area adjacent the upper protectivelayer 110 and the frame half 180. After some time, these liquids candeteriorate the upper protective layer and/or the half frame, and leakinto the module itself, shorting-out one or more of the solar cells.Another known problem with prior designs is that often the bottom framehalf 180 is thicker than pressure sensitive adhesive (PSA) tape layer160, thus reducing the ability of the module 100 to stick securely tothe roof around the frame of the module. Thus, what is needed is aphotovoltaic module with improved edge seal design to prevent suchliquid damage and to enhance the ability of the module to stick to theroof.

SUMMARY OF THE INVENTION

The photovoltaic module described herein and illustrated in the attacheddrawings enables the electricity-generating solar module to be installedon an existing flat or tiled roof, and prevents theliquids/solids-damage noted above. In particular, the module edge sealis tapered away from the module surface, so that water and other liquidsand/or solids are deflected off of the module and are not retained onthe surface thereof.

In accordance with one aspect of the present invention, a photovoltaicmodule has an upper transparent protective layer, and a photovoltaiclayer positioned beneath the upper transparent protective layer. Thephotovoltaic layer includes a plurality of electrically interconnectedphotovoltaic cells disposed in an array. A rigid substrate layer ispositioned beneath the photovoltaic layer. A tapered edge seal isdisposed (i) adjacent the photovoltaic layer, (ii) above the rigidsubstrate layer, and (iii) beneath the transparent protective layer. Thetapered edge seal is thinner at an outer peripheral portion thereof thanat a portion thereof adjacent the photovoltaic layer. An adhesion layerhas a first surface attached to an exposed lower surface of the rigidsubstrate layer, and has a second surface for adhering the module to aroofing surface.

In accordance with another aspect of the present invention, aphotovoltaic module has an upper transparent layer, and a photovoltaiclayer positioned beneath the upper transparent layer. The photovoltaiclayer includes (i) a plurality of electrically interconnectedphotovoltaic cells disposed in a two-dimensional array and (ii) anelectrical junction box on the same side of the module as the array ofcells. A first layer of heat-activated transparent adhesive isinterposed between the upper transparent layer and the photovoltaiclayer to adhere the photovoltaic layer to the upper transparent layer. Arigid layer is positioned beneath the photovoltaic layer. A second layerof heat-activated transparent adhesive is interposed between thephotovoltaic layer and the rigid layer to adhere the photovoltaic layerto the rigid layer. An edge seal is disposed about a periphery of themodule, beneath said upper transparent layer, above said rigid layer,and beside said photovoltaic layer. The edge seal is thicker adjacentthe photovoltaic layer than at an outermost edge of the edge seal.

In accordance with a further aspect of the present invention, a methodof making a tapered edged photovoltaic module includes: (i) disposing aphotovoltaic layer on a rigid substrate, the rigid substrate being widerand longer than the photovoltaic layer; (ii) forming a tapered edge sealsideways adjacent the photovoltaic layer such that (i) an outer edge ofthe tapered edge seal is co-extensive with an outer edge of the rigidsubstrate, and (ii) the tapered edge seal tapers downward from the areaadjacent the photovoltaic layer to the outer edge of the rigidsubstrate; and (iii) forming a protective layer over the photovoltaiclayer to prevent water and moisture ingress.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain aspects in accordance with embodiments of the present inventionare described below in connection with the accompanying drawing figuresin which:

FIG. 1 illustrates a perspective view of a first embodiment of alaminated photovoltaic module according to the present invention.

FIG. 2 illustrates a top view of the photovoltaic module of FIG. 1 withjunction box showing conductors;

FIG. 3 illustrates a bottom view of the photovoltaic module of FIG. 1;

FIG. 4 illustrates an end view of the photovoltaic module of FIG. 1;

FIG. 5 illustrates a side view of the photovoltaic module of FIG. 1;

FIG. 6 illustrates a perspective view of another embodiment of alaminated photovoltaic module according to the present invention;

FIG. 7 illustrates a cross section view of photovoltaic modules of FIG.1 and FIG. 6;

FIGS. 8a and 8b illustrate close-up top views of the edge seals of thelaminated photovoltaic modules of FIG. 1 and FIG. 6, respectively;

FIG. 9 illustrates a pattern for placing adhesive tape on the back ofthe photovoltaic module of FIG. 1; and

FIG. 10 illustrates a pattern for placing adhesive tape on the back ofthe photovoltaic module of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in FIGS. 1, 2, 3, 4, and 5, a laminated photovoltaicmodule 100 is preferably configured as a generally rectangular module,which is sized and shaped in accordance with the sizes and shapes ofconventional building materials, such as a 4×8 foot module. Thus, themodule 100 can be handled by a construction crew without requiring anyspecial material handling equipment. Of course, the module 100 may beany convenient size (4×8, 4×4, 3×3, 3×2, 2×2, 2×1, 1×1, etc.), and shape(square, round, triangular, trapezoidal, etc.) useful in theconstruction industry, and with either rounded corners or substantiallyright angle corners. The module 100 is preferably assembled in a factoryor other suitable environment so that the module 100 is complete andready to install on a substantially flat roof (which may be horizontalor tilted), or sloped shingle roofs, such as, but not limited to,asphalt, laminated, wood, slate, or other location having adequateexposure to the sun. In one preferred embodiment, as shown in FIGS. 1,2, 3, 4, and 5, the module 100 has dimensions of approximately 101centimeters (−40 inches) by 196 centimeters (−77 inches) and has athickness of approximately 0.5 centimeter (0.2 inch). In anotherpreferred embodiment, as shown in FIG. 6, the module 100 has dimensionsof approximately 101 centimeters (−40 inches) by 101 centimeters (−40inches) and has a thickness of approximately 0.3 centimeter (⅛ inch)when installed. In fact, the thickness of the module is preferably thesame as (or thinner than) the thickness of the laminated roofingshingle. Thus, the module 100 does not add significant height to a roofstructure and will not block water flow on sloped roof. In yet anotherembodiment, the module 100 has dimensions of approximately 101centimeters (−40 inches) by 239 centimeters (−94 inches) and has athickness of approximately 0.5 centimeter (0.2 inch).

As shown in FIG. 7, the module 100 preferably has a transparent upperprotective layer 110 that faces upward and is exposed to the sun. Amiddle layer 120 is preferably positioned beneath the upper protectivelayer 110. The middle layer 120 comprises a plurality of photovoltaiccells 122 electrically interconnected to form a photovoltaic array. Themiddle layer 120 preferably rests on a rigid lower substrate 130. Themiddle layer 120 is preferably secured to the rigid lower layer 130 by alower adhesive layer 140. The middle layer 120 is preferably secured tothe upper protective layer 110 by an upper adhesive layer 150. Themiddle layer 120 is thus encapsulated between the lower adhesive layer140 and the upper adhesive layer 150.

The upper protective layer 110 preferably provides impact protection aswell as weather protection to the module 100. The upper protective layer110 advantageously comprises of a transparent flexible polymer material,such as, but not limited to Ethylene tetrafluoroethylene (ETFE), afluorine based co-polymer, which is formed into a film layer of suitablethickness (e.g., approximately 0.005-0.013 centimeter (0.002-0.005inch)). Thus, the photovoltaic cells 122 in the middle layer 120 areexposed to direct sunlight without being exposed to moisture and otherclimatic conditions and without being exposed to direct impact by feet,falling objects, and debris. Tempered glass having a suitable thicknessmay also be used as the upper protective layer 110.

In the illustrated embodiment of FIGS. 3, 4, and 5, the rigid lowerlayer substrate 130 preferably comprises fiber reinforced plastic (FRP).For example, the FRP layer 130 advantageously comprises a polyesterresin with embedded stranded glass fibers. Preferably the said FRP layerhas a thickness of approximately 0.1 centimeter to 1 centimeter (0.079inch-0.39 inch), and additionally, the said FRP lower surface can beeither flat or with a defined pattern/rib. The lower layer 130 of FRPthus provides an advantageous combination of rigidity, light weight,very low permeability, and flatness.

Preferably, the lower adhesive layer 140 is provided as a thin film thatis positioned on the upper surface of the rigid lower layer 130. Thearray of photovoltaic cells 122 in the middle layer 120 is thenpositioned on the lower adhesive layer 140. In the illustratedembodiment, the lower adhesive layer 140 advantageously comprises atransparent adhesive, such as, for example, ethylene-vinyl-acetate(EVA). EVA is a transparent, heat-activated adhesive that isparticularly suitable for securing the cells. Other suitable adhesives,such as, for example, polyvinylbuterol (PVB), thermoplastic poly-olefin(TPO), Silicone, Ionomers, reactive poly-olefin (PO) or other pottantmaterials, can be substituted for the EVA. In a preferred embodiment, alayer 142 (FIG. 7) of DuPont™ Tedlar™ is disposed between the substrate130 and the middle layer 120 (in addition to adhesive layer 140).Tedlar™ is a highly versatile polyvinyl fluoride film (PVF) thatprovides a long-lasting finish to a wide variety of surfaces exposed toharsh environments.

The preferred embodiment provides an improved design and implementationof a tapered edge seal 99 for photovoltaic modules. The tapered edgeseal design replaces the thick edge rim 180 (shown in U.S. Pat. No.7,531,740) around the periphery of the module with a seal material.Thus, the new design is “frameless.” The seal 99 is preferably formed asa seamless structure around the outer peripheral edges of the module 100(see FIGS. 2 and 7). The seal 99 may comprise a sloped portion of layer110, but is more preferably a section of tapered material (to bedescribed below) sandwiched between the flexible thin film superstrate110 (0.025 mm to 0.1mm thick) and the rigid substrate 130, and bonded toboth the superstrate and the substrate on top and bottom surfaces of theseal 99, as will be described in greater detail below with respect tothe embodiment of FIG. 7. Alternatively, the seal 99 may be bonded tothe side of middle layer 120 by, preferably, an encapsulation materialon the inner face of the seal 99. The outer face of the seal 99 ispreferably exposed to ambient, but may be covered with a protectivelayer, such as an extension of protective layer 110. Alternativeembodiments may include any combination of: the layer 110 not extendingover top of the seal 99; the layer 110 extending to the edge of themodule 100, beneath the seal 99, but on top of the substrate 130; thelayer 110 extending downward on the outer-facing surface of the middlelayer 120, but not beneath the seal 99; and/or portion(s) of protectivelayer 110 enclosing seal 99 may comprise a flat portion (0-50%) of seal99 width and a sloped portion of (100-50%) of seal 99 width (as measuredfrom the edge of the middle layer 120.

The tapered seal design thus removes the former rim on the top surfaceof the module 100, and thus eliminates water and dust trapped on theside edge of the top surface of layer 110. In addition, the tapered edgeseal design preferably incorporates the flexible nature of thesuperstrate 110 that generates a gradual profile on the edges of themodule that helps water run off (see FIG. 7). Furthermore, this designdoes not add any profile on the bottom face of the module 100, and thisallows module 100 to be somewhat more flexible, allowing the module tobe more closely conform to the roof surface, which may not be completelyflat. Thus, the module 100 according to the present invention may besafely installed on non-flat surfaces.

An additional benefit for the tapered edge seal design is that themodule's back side is flat (without a frame edge), and thus a thinnerpressure sensitive adhesive (PSA) tape can be employed (as shown inFIGS. 9 and 10). Currently, thicker PSA tape is required due to edge rimthickness on the backside of the modules, as shown in FIG. 1 of U.S.Pat. No. 7,531,740. PSA tape for modules with the tapered edge sealdesign may be applied in the same pattern as for the module with theedge rim. The difference for applying PSA tape on modules with thetapered edge seal is that the tape may now lay closer to the edges ofthe substrate, as shown in FIG. 9.

Preferably; the edge seal 99 is comprised of a polymeric material whichis water resistant and a gas ingress barrier (with low gas permeationrate), and is UV resistant. The seal material should show strongadhesion to both superstrate and substrate surfaces. The edge seal 99can be either in the form solid tape or liquid paste. When in tape form,the edge seal preferably has a width ranging from 10 mm to 25 mm and athickness from 1 mm to 2 mm. A preferred edge seal tape is HelioSeal™PVS 101 from ADCO, Michigan Center, Mich. HelioSeal™ PVS 101 is asynthetic polymer based sealant with integrated desiccant for moisturetrapping. It is possible for the edge seal material to comprise one ormore of the materials comprising the middle layer 120.

One edge seal embodiment is shown in FIG. 7, which is a schematic,partial, cross-sectional view of the module 100 that shows the edge seal99 design configuration (not to scale). The edge seal 99 is preferablybonded on its lower surface to substrate 130 (and/or on top of adhesivelayer 140). And/or the inner face of seal 99 may be bonded to an outerface of the encapsulated middle layer 120. And/or the upper face of theedge seal 99 may be bonded to a lower surface of the upper protectivelayer 110 (although the upper face 99 could be bonded to a lower face ofadhesive layer 150). As can be seen in FIG. 7, the edge seal 99 tapersaway from the middle layer 120 toward the outer peripheral edge of themodule 100. As can be seen in FIGS. 4 and 5, the taper is preferably3-10 degrees of slope (more preferably 4-9 degrees, even more preferably5-8 degrees, and 6-7 degrees most preferred), beginning at about 0-30percent of the distance from (i) the interface of the edge seal 99 andthe middle layer 120 and (ii) the outer edge of the module 100.

As shown in FIG. 8a , each corner of the module 100 is preferablyradiused around the corners, making a smooth transition from one edge ofthe module 100 to the other. The corner surface of the tapered edge seal99 thus presents a shallow, partial, shallow, quarter frusto-conicalshape. If tape is used for the edge material instead of a liquid orpaste, an overlap of tapes at the corners is preferred to eliminateseams in the edge seal at the corners, in order to minimize possiblewater and moisture ingress. As shown in FIG. 8b , the corner of themodule 100 may have a more right-angle configuration, with the seal 99presenting a sharper, partial, quarter frusto-conical shape.

FIGS. 9 and 10 show various configurations for peel-and-stick tape 160to be applied to the bottom surface of the substrate 130. In FIG. 9, thePSA tape 160 is preferably applied to the peripheral edges of the module100, preferably together with one or more vertical and/or horizontalstripes across the module bottom face. This is a preferred embodimentfor flat roof application. In FIG. 10, a number of squares (orrectangles) of PSA tape 160 are affixed to the bottom surface of themodule 100, preferably in a matrix array (4 columns by 7 rows in thedisclosed embodiment). This is a preferred embodiment for sloped shingleor tile roofs. Alternatively, the PSA tape 160 can be applied in two ormore horizontally (or vertically) extending stripes of tape.

The edge seal material is preferably incorporated in photovoltaicmodules in a process that will be described in greater detail below, butgenerally comprises positioning the tape seal 99 on the substrate 130along the edges of the substrate with the middle layer 120 disposedwithin (inside) the edge seal on the substrate 130. The rest of thelayup process is substantially the same as will be described below. Theassembly is laminated through a vacuuming thermal compression processcommonly used in crystalline silicon PV module manufacturing process.The seal material 99 preferably forms a seamless frame around the moduleedges after the process. The process produces a flat top surface with agradual profile on the edges and without a rim at module edges.

In FIG. 7, in greater detail, a Tedlar layer 142 is positioned over thetop surface of the substrate 130, and the adhesive layer 140 is placedon top of the Tedlar layer 142. After positioning the array ofphotovoltaic cells 122 on the lower adhesive layer 140, the uppertransparent adhesive layer 150 is placed over the middle layer 120 sothat the photovoltaic cells 122 are sandwiched between the twotransparent adhesive layers 140 and 150. Preferably, the upper adhesivelayer 150 should match the physical characteristics of the loweradhesive layer 140. In the illustrated embodiment, both the upperadhesive layer 150 and the lower adhesive layer 140 comprise EVA, butother suitable transparent adhesives can be substituted for the EVA. Theedge seal 99 is preferably then applied to the outer peripheral edges ofthe module 100, outside the encapsulated middle layer 120. Then, thetransparent upper protective layer 110 is positioned over the uppertransparent adhesive layer 150 and the edge seal 99 to complete thestructure shown in an enlarged partial cross section in FIG. 7.Alternatively, module layup could start from laying down first the upperprotective layer 110, followed by (in order) upper transparent adhesivelayer 150, photovoltaic cells 122, and lower adhesive layer 140. Edgeseal 99 placements follow the same procedure as stated above, and lastsubstrate 130 is placed.

The EVA material and the use of the EVA material to bind the layers of alaminated photovoltaic cell are described, for example, in U.S. Pat. No.4,499,658 to Lewis (incorporated herein by reference). In addition toacting as a binder to secure the photovoltaic cells 122 between theupper protective layer 110 and the lower rigid layer 130, the upper EVAlayer 150 and the lower EVA layer 140 also act as cushions between thetwo outer layers.

The photovoltaic cells 122 are electrically interconnected in aseries-parallel configuration in a conventional manner to provide asuitable output voltage or a desired photovoltaic module form factor.For example, FIGS. 1 and 2 show a photovoltaic module suitable for flatroof application. Photovoltaic cells 122 are arranged in 6 rows of 12cells each; FIG. 6 shows a square-shaped photovoltaic module suitablefor sloped residential composite shingle roof applications. Photovoltaiccells 122 are preferably arranged in 6 rows of 6 cells each; however,one, two, or more cells are preferably omitted from the uppermost row toprovide room for positioning an electrical enclosure, such as, but notlimited to junction box 170 (having a first weather-resistant electricalconductor 172 and a second weather-resistant electrical conductor 174),module power optimizer, micro inverter, and other useful electricalcontrol and/or power-conditioning circuitry. The photovoltaic module 100preferably includes two module output conductors 176, 178 (e.g., FIG. 2)that extend from the top surface of the middle layer 120 in the area ofthe omitted photovoltaic cell(s). Each of the module output conductors176, 178 is preferably connected to a respective one of theweather-resistant electrical conductors 172, 174 within the electricalenclosure 170 after the photovoltaic module 100 is laminated, asdiscussed below.

For the lamination process, the upper protective layer 110, the middlelayer 120, the lower layer 130, the two adhesive layers 140 and 150, andthe Tedlar™ layer 142 have been stacked and are aligned to form thesandwich structure, as discussed above in FIG. 9 as well as FIG. 6. Theedge seal material is then applied, as also discussed above. The freeend of each of the module output conductors 176, 178 are preferablycovered with a temporary covering (e.g., a PVFE, or the like) during thelamination process. The structure is permanently laminated in a knownmanner using heat and pressure. In one advantageous embodiment, thestructure is laminated in a vacuum laminator in the manner described,for example, in US Patent Application Publication No. 2005/0178248 A1 toLaaly et al (incorporated herein by reference). In particular, thestructure is first subjected to a vacuum to remove any trapped gasbubbles in the EVA adhesives. The structure is then subjected to highpressure to force the layers together as tightly as practicable. Thestructure is then heated to a suitable temperature (e.g., approximately150 degrees C.) to cure the adhesives in the layers 140 and 150 andthereby permanently bond the adjacent layers.

The laminated structure is preferably held at the high temperature for asufficient time to cure the upper transparent adhesive layer 150 and thelower transparent adhesive layer 140, and to cause the two transparentadhesive layers to adhere together to become a combined layer thatcompletely encapsulates the photovoltaic cells 122. The high temperaturealso causes the upper transparent layer 110 and the edge seal 99 tosoften and flow to provide the protective upper coating and the edgeseal described above. The laminated structure is then allowed to cool toambient temperature.

As shown in FIG. 10, the preferred method of installation of the module100 on a composite shingle roof comprises applying a layer 160 of PSAtape to the bottom surface of the rigid lower layer 130. Positions ofthe PSA tapes are designed for common roof shingle course width,nominally about 5½ inches apart. Preferably, the tape layer 160comprises a suitable double-stick tape, such as, for example but notlimited to, a self-sealing tape having a formulation of resins,thermoplastics, curing rubbers, and non-curing rubbers. The double-sticktape has adhesive on both sides. When manufactured, the double-sticktape has a release layer on each side to prevent adhesion. One releaselayer is advantageously removed during the process of manufacturing themodules. The exposed adhesion side of the tape layer 160 is positionedon and adhered to the bottom surface of the rigid lower layer 130 beforeshipping the module 100. Then, during installation of the module 100,the remaining release layer is removed so that the module can be adheredto the surface of an existing roof. The surface of the existing roof iscleaned and suitably prepared to receive the module 100. Afterinstallation, suitable pressure is applied to the upper layer 110 of themodule 100 to permanently adhere the module to the surface of the roof.In one preferred embodiment, The PSA tape 160 is 4″ by 4″ squares ofButyl tape. Preferably, the lower edge of the butyl tape is alignedapproximately with the lower edge of each shingle course forinstallation, but the upper edge of the butyl tape may be spacedsomewhat from the top edge of the module 100.

The present invention is disclosed herein in terms of a preferredembodiment thereof, which provides an exterior building module asdefined in the appended claims. Various changes, modifications, andalterations in the teachings of the present invention may becontemplated by those skilled in the art without departing from theintended spirit and scope of the appended claims. It is intended thatthe present invention encompass such changes and modifications.

What is claimed is:
 1. A photovoltaic module, comprising: an uppertransparent protective layer; a photovoltaic layer positioned beneaththe upper transparent protective layer, the photovoltaic layercomprising a plurality of electrically interconnected photovoltaic cellsdisposed in an array; a rigid substrate layer positioned beneath thephotovoltaic layer; a tapered edge seal disposed (i) adjacent thephotovoltaic layer, (ii) above the rigid substrate layer, and (iii)beneath the transparent protective layer, said tapered edge seal beingthinner at an outer peripheral portion thereof than at a portion thereofadjacent the photovoltaic layer; and an adhesion layer having a firstsurface attached to an exposed lower surface of the module, and having asecond surface for adhering the module to a roofing surface.